title: Identification of the predominant nonrestoring allele for Owen-type cytoplasmic male sterility in sugar beet (Beta vulgarisL.): development of molecular markers for the maintainer genotype.
abstract: Hybrid seed production in sugar beet relies on cytoplasmic male sterility (CMS). As time-consuming and laborious test crosses with a CMS tester are necessary to identify maintainer lines, development of a marker-assisted selection method for therfgene (the nonrestoring allele ofrestorer-of-fertilitylocus) is highly desirable for sugar-beet breeding. To develop such a method, we investigated genetic variation at theRf1locus, one of twoRfloci known in sugar beet. AfterHindIII-digestion, genomic DNAs from beet plants known to have a restoringRf1allele yielded a range of hybridization patterns on agarose gels, indicating thatRf1is a multi-allelic locus. However, the hybridization patterns of 22 of 23 maintainer lines were indistinguishable. The nucleotide sequences of therf1coding regions of these 22 maintainer lines were found to be identical, confirming that the lines had the samerf1allele. Two PCR markers were developed that targeted a downstream intergenic sequence and an intron ofRf1.The electrophoretic patterns of both markers indicated multipleRf1alleles, one of which, named the dd(L) type, was associated with the maintainer genotype. To test the validity of marker-assisted selection, 147 sugar beet plants were genotyped using these markers. Additionally, the 147 sugar beet plants were crossed with CMS plants to determine whether they possessed the maintainer genotype. Analysis of 5038 F1 offspring showed that 53 % of the dd(L) plants, but none of the plants with other alleles, had the maintainer genotype. Thus, selection for the dd(L) type considerably enriched the proportion of plants with the maintainer genotype.
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, N-9, W-9, Kita-ku, Sapporo, 060-8589 Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Moritani
authors.forename: Kazunori
authors.initials: K
authors.lastname: Taguchi
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Kitazaki
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsuhira
authors.forename: Takaya
authors.initials: T
authors.lastname: Katsuyama
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Mikami
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Kubo
keywords: Genetic association; Marker-assisted selection; Multi-allelic locus; PCR marker; Restorer of fertility